Eouse electric



' TN SSES: INVENTOR f? BY Nov. 9 1926. 1,606,029

H. T. HERR BLADE FASTENING Filed March 6, 1925 ATTORNEY Patented Nov. 9,1926 hairs srres lesser HERBERT 'i". HERB, OF PHILADELPHIA,PENNSYLVANIA, ASSIGNOR T0 vW'ESitlillllGr- HOUSE ELECTRIC &MANUFACTURING COMPANY, A, CORPORATION OF FENNSYL- VANIA.

BLADE FASTENING.

Application filed. March 6, 1925. Serial No. 13,659.

means for use in turbines and it has for its object to provide apparatusof the character designated which shall be effective to tightly retainblades in place over long periods of time and under widely varyingtemperature conditions, it being more specifically adapted for use inconnection with blades having a relatively high coeflicient of linearexpansion when mounted in blade-holding slots formed of material havinga relatively low coefficient of linear expansion.

In the accompanying drawing, Fig. 1 is a sectional view ofja portion ofa blade-holding member embracing a blade root and constructed inaccordance with one form of my invention, the mounting shown beingparticularly adapted for the mounting of fixed blades; Fig. 2 is a topview, partially in section and partially in elevation, of a portion ofthe blade row taken on the plane II-II in Fig. 1 and more clearlyindicating the arrangement of the packing means of Fig. 1; Fig. 3 is aview similar to Fig. 1 andillustrating a blade mounting structureparticularly adapted for moving blades; and Fig. 4. is a view similar toFig. 3 but showing an alternative form of packing member, the lat terbeingshown more fully in Fig. 5.

In the construction of elastic fluid turbines, it is usual to form theblade-holding members of cast iron or steel and it has been proposed toemploy blades of relatively large size formed from material having arelatively high coeflicient of expansion such, for example, as phosphorbronze. When blades of this character are fastened by rigid packingmeans in slots formed in material having a relatively low coetficient ofexpansion, such as iron or steel, it will be obvious that upon heatingthe structure, the relatively great coefficient of expansion of theblade material tends to crush the packing means, repeated heating andcooling resulting in loosening up the entire packing structure.

In accordance with the present invention, I employ packing means soformed as to have an appreciable amount of resilience, whereby the bladeroot may expand and contract to a greater degree than the mate:

rial of the blade-holding member without crushing the packing materialand without eventual loosening of the entire packing tailedunderstanding of my invention, I show aportion of the casing or statorof a steam turbine at 10 in Fig. 1, this member being provided with aslot 11 in which is placed the root 12 of a blade 13.

A small slot 14 is formed in the side wall of the main slot 11 anddirectly opposed thereto is a notch 15 in the blade root.

A packing member 16 of serpentine shape, as more clearly shown in Fig.2, is inserted in the space formed by the slot 14: and the notches 15 insuccessive blades, the pitch of the convolutions in the member 16 beingthe same as the blade pitch so that a hump of the packing member restsagainst each blade root, bearing against the slot wall being securedintermediate the adjacent blade roots of a row, as indicated at 21.

Inasmuch as the packing member 16 must be inserted at a given point onthe casing and driven around through the slot to its point of final use,it will be obvious that the member 16 cannot be formed out of sectionshaving undue length. I have illus trated in Fig. 2 the use of a memberhaving a length equivalent to the pitch of two blades and I have alsoshown amember 16 having a length equal to the pitch of one blade,

either form operating satisfactorily when driven into final position andthe lengths actually employedbeing determined by the conditions of thedesign.

In order to further enhance the rigidity of the blade fastening, I mayemploy the usual end packing shown at 17. v

In the mounting of a blade in the rotor structure of a turbine, it isnecessary to pro- ,vide for centrifugal stresses which are notencountered in a fixed blade and accordingly, as shown in Fig. 3, Iprovide a slot 11 ma blade-holding member 10, said slot being providedwith overhanging portions 18 and 19 in the walls thereof so as toprovide an undercut portion at the base of the slot .11.- The blade root1-2? is correspondingly notched so as to engage in the undercut slot,

all as is well-known and understood in the art, and the blade slot 11 isfurther provided with a packing groove 14 in the wall thereofimmediately above the member 19. A packing member 15 is inserted in theslot 14: for a function similar to that explained in connection withFig. 1. It is preferable to place the packing means above thedovetailedinterolck inasmuch as the ion rigid holding of the blade nearits point of emergence from the holding member d1- minishes the bendingstralns on the reduced neck portion of the blade, thus increasingsection as clearly shown in perspective at 20 in Fig. 5.

Having thus described the arrangement of apparatus embodying myinvention, the operation is as follows The blades being formed ofphosphor bronze or other material having 'a higher coefiicient ofexpansionthan the iron or steel forming the bladerholding means, tend toexpand more than the slot upon an increase in temperature and to alsocontract more than the slot upon a decrease in temperature. lVith theform of packing shown either in Fi 2 or in Fig. 5, the points of bearingagainst the blade root are not directly opposite the points of bearingagainst the side wall of the slot so that the packing member ispermitted to be deformed under pressure and to reassume its originalshape uponthe removal of such pressure. Thus, the packing means hold theblade root in firm engagement with the slot throughout constantlyrecurring temperature changes over long periods of time.

l Vhile I have shown my invention in several forms, it will be obviousto those skilled in the art that itis not so limited, but is susceptibleof various other changes and modifications, without departing from 'thespirit thereof, and I desire, therefore, that only such limitationsshall be placed thereupon as areimposed bythe prior art or as arespecificallyset forth in the appended claims. V

What I claim is:

1. In a turbine, the combination of bladeholding structure having ablade-root groove, one side wall ofsaid groove being provided with aslot, a row of blades having root portions fitting in the groove, andmeans in said groove resiliently urging said blade root against theopposite side wallof the groove.

2. The combination defined in claim 1 wherein the blade root hasinterlocking engagement in the groove in a plane normal to the bladeaxis for retaining the blade root in the groove.

3,111 aturbine, the combination of blade-holding structure having ablade- .root groove, one side wall of said groove being provided with aslot, a row of blades havingroot portro-nsfittmg 1n the groove, andresilient packing means in sa d slot for gagement in the groove in aplane normal to the blade axis for retaining the blade root in thegroove.

5. In 'a mounting for turbine blades, a blade-holding member, a turbineblade, a slot in the blade-holding member adapted for the reception ofthe blade root and a packing member tightly fitting between the bladeroot and one side wall of the slot, the

points of contact of said packing member against said blade root beingspaced away from direct opposition to the points of contact of saidpacking member against said slot wall, whereby the resilience of saidpacking member is effective in a lateral direction to force said bladeroot against the opposite sidewall of the slot.

6. In a. mounting for turbine blades, the combination with ablade-holding member having an undercut slot therein, of a bladeprovided with an enlarged root for. engaging in said slot and a packingmember tightly fitting between the blade root and one side wall of theslot, the points of contact of said packing member against said bladeroot being spaced away from direct opposition to the points of contactof said packing member against said slot wall, whereby the resiliencevof said packing member is ef fective in a lateral direction to forcesaid blade root against the opposite side wall of the slot.

7. In a turbine, the combination with a blade-holding member having agiven coefiicient of linear expansion and provided with a blade holdingslot, of a blade disposed in said slot, and having a greater coeflicientof linear expansion, and packing means disposed between the blade rootand one side wall of the slot and adapted to maintain tight engagementbetween said blade root and the opposite slot wall under varyingtemperature conditions.

8. In a turbine, the combination of blade holding structure having ablade-root groove, a row of blades having root portions fitting in thegroove, said groove and said root portions being provided withregistering lateral slots, and a resilient packing member in the slotsfor holding the blades in place with respect to said structure, theresilience of said packing member being effective in a lateral directionto force the blades against the, opposite wall of the groove.

9. The combination of a turbine blade, a

bladediolding member having a slot therein for the reception of theblade root, registering slots in meeting walls of the blade root and thefirst-mentioned slot, and a resilient packing member enclosed by saidregistering slots,- said packing member locking the blade againstoutward movement and also forcing said blade root against the oppositewall of the first-mentioned slot.

10f The combination described in claim 9 and a packing member betweenthe bottom of the first-mentioned slot and the bottom of the blade root.I

11. The combination of a turbine blade, a blade-holding member having aslot therein for the reception of the blade root, an inwardly facingshoulder in one side wall of the slot and an outwardly-facing shoulderin the adjacent wall of the blade root, and a packing member disposedbetween said walls and between said shoulders, thereby locking bladeroot against the opposite wall of the slot.

In testimony whereof, I have hereunto 2U subscribed my name thiseleventh day of February, 1925.

HERBERT T. HERB.

